BT: Don't answer video call as audio only call.

Use case:
1. Connect BT headset.
2. Receive MT video call.
3. Answer using BT headset.

Failure:
Video call gets answered as audio only call.

Root cause:
When answering call from BT headset, we are not checking
the if the call is video call and answering it as audio call.

Fix:
Check if the call is video call when answering with BT headset.

Change-Id: I9f29fee5685302046b2ac3f87e4b844150152a49